HVAC Questions? Ask an HVAC Expert for Answers ASAP
Hello, Is the metering device an expansion valve or an orifice type fixed capillary? If it is an expansion valve, have you tried adjusting the superheat?
I am not sure. How do I check? I've heard the contractor mentioning the term orifice.
I am pretty handy, so whatever I can do I don't mind doing...
Hello, If the metering device is a fixed orifice, then it is not adjustable. You can not do anything to adjust the super heat of the unit.
Can you enlighten me please. You mention of a contractor, I am thinking you are the contractor. SO, if you are the customer, and you are not satisfied, can you not contact your contractor and tell him you still have issues with the conversion?
If you are the customer, then adjusting the super heat would be expensive since you would need hvac tools to do that. It should be done by an HVAC engineer.
Hello, I opened up the cover of the evaporator, it's definitely an orifice and a bunch of small tubes leading to the main evaporator. I am a customer, not a contractor. Why would you think I am a contractor?
Because of the many questions that you have placed here on the site. Some contractors are doing it here. Anyway, So, it is an orifice so we can not adjust the super heat.
Anyway, I was adding more refrigerant little by little while observing the temperature and freezing of the evaporator. As I reached 48 psi (190 psi on high side), the evaporator stopped freezing, and most of it maintained pretty cool temperature around 40 degrees. So, based on my experience with this unit, the optimal temparature is 48 degrees. Above that, the avaporator produces little cold, while below that it starts freezing. Based on this information, would replacing an orifice with larger or smaller flow orifice be beneficial?
I would say, stop on the 48 psi where the temp of the inlet tubes are coldest. Would you know the temperature of the outlet tubes of the evaporator coil?
Yes, I measured all of them, and the range is 35-45 degrees. The further from the capillars, the higher the temperature, and vice versa. I have another small practical question. While I am disconnecting the high pressure hose, a lot of the refrigerant escapes by the time I completely unscrew the cap and the valve closes. What is the right technique?
Was there a valve on the high pressure side? Or it is just a shreader valve like the one on tires?
Just like on tires, and just like on the low pressure side.
Ok. What I can suggest is to turn the unit off , let the pressure stabilize, then hold the hose downward towards the pipe while loosening the round fitting of the hose. If you know that the whole fitting is unscrewed, let go of the hose and remove it. A small amount of liquid would come out but not sticking the valve open and letting a lot of liquid refrigerant flow out. I suggest use gloves to prevent frost bite.
By the way, did the contractor flush the system from its old oil?
When I say the outlet tubes of the evaporator, I mean the tubes that comes out of the evaporator going to the compressor. That would be the big pipe as all of the other pipes connects together and comes out as one. That would be the pipe to measure the temperature. Then we can compute the super heat.
Also, when you are adding refrigerant, use the liquid from the tank to add the refrigerant. R-407 gas has different blends form its liquid form and liquid is needed to charge a system.
Hello....are you still here?....
Hello, I am sorry but I have to leave. I will check again later and see if you have responded. With your question if you need a bigger orifice or a smaller, we need to find out what is the temperature of the outlet pipe first in order to find out what is the super heat so we can decide if we need a bigger orifice. Thanks
Hello again, sorry I didn't realize you responded...
Thank you for the recommendation on disconnecting the high pressure hose. That's what I was thinking. And yes, at least I figured to use gloves. They were all frozen.
When I was charging, I was moving the can around to make sure the content is mixing. But I kept it vertical, so I am pretty sure it was gas and not liquid entering the system. Now I recal the contractor putting the can on its side, and now I understand why.
I think the contractor flusshed the system. He was using some sort of compressor connected to it. I wasn't watching all the time.
The temperature of the retrun tube at the compressor was around 50-55 degrees, but I am not sure. Would need to measure later on...
Russ, thank you. Type of refrigerant was not my choice.
Thanks for your suggestions. Over the weekend, I found the sweet spot which corresponds to 48 psi. I followed the same logic you mentioned - gradually adding refrigerant to the point the orifice and capillars stop freezing. It's been cooling for two days now, and with good results. In order to replace orifice, I would neet to call the contractor who will charge me for all the work and for an additional refrigerant to recharge the system. I will see if I can get away with how it performs now. Thanks again.